Properties, evolution and morpho-kinematical modelling of the very fast nova V2672Oph (NovaOph2009), a clone of USco

ovaOph2009 (V2672Oph) reached maximum brightness V= 11.35 on 2009 August 16.5. With observed t2(V) = 2.3 and t3(V) = 4.2d decline times, it is one of the fastest known novae, being rivalled only by V1500Cyg (1975) and V838Her (1991) among classical novae, and USco among the recurrent ones. The line of sight to the nova passes within a few degrees of the Galactic Centre. The reddening of V2672Oph is E(B-V) = 1.6 ± 0.1, and its distance d 19 kpc places it on the other side of the Galactic Centre at a galactocentric distance larger than the solar one. The lack of an infrared counterpart for the progenitor excludes the donor star from being a cool giant like in RSOph or TCrB. With close similarity to USco, V2672Oph displayed a photometric plateau phase, a He/N spectrum classification, extreme expansion velocities and triple peaked emission-line profiles during advanced decline. The full width at zero intensity of Hα was 12000kms-1 at maximum, and declined linearly in time with a slope very similar to that observed in USco. The properties displayed by V2672Oph lead us to infer a mass of its white dwarf close to the Chandrasekhar limit and a possible final fate as a Type Ia supernova. Morpho-kinematical modelling of the evolution of the Hα profile suggests that the overall structure of the ejecta is that of a prolate system with polar blobs and an equatorial ring. The density in the prolate system appeared to decline faster than that in the other components. V2672Oph is seen pole-on, with an inclination of 0°± 6° and an expansion velocity of the polar blobs of 4800+900-800kms-1. On the basis of its remarkable similarity to USco, we suspect this nova may be a recurrent. Given the southern declination, the faintness at maximum, the extremely rapid decline and its close proximity to the ecliptic, it is quite possible that previous outbursts of V2672Oph have been missed. [PUBLICATION ABSTRACT]